1. Field
The presently disclosed subject matter relates to a vehicle lamp including a projector headlight for a low beam, and more particularly to a vehicle lamp including a projector headlight having a favorable light distribution pattern that can conform to a light distribution standard for a headlight with respect to a contrasting difference between the upper and lower sides of a horizontal cut-off line in the light distribution pattern.
2. Description of the Related Art
A projector headlight for a low beam and/or a high beam is frequently incorporated into a vehicle lamp including a position lamp, a turn-signal lamp, etc. The projector headlight may allow a light-emitting area thereof to be reduced and therefore allows the vehicle lamp including the projector headlight to be minimized in comparison with other type headlights.
A conventional projector headlight for a low beam is disclosed in patent document No. 1 (Japanese Patent No. 2696745). FIG. 20(A) is a perspective exploded diagram depicting a structure of a conventional projector headlight disclosed in patent document No. 1 and FIG. 20(B) is a schematic diagram showing a fundamental light distribution pattern of the conventional projector headlight when drivers keep to the right side of the road.
According to the conventional projector headlight 20 shown in FIG. 20(A), the projector headlight 20 includes: a light source 21; an elliptical reflector 22 in which a first focus thereof is located near the light source 21; a projector lens 24 which has a focus thereof located near a second focus of the elliptical reflector 22; and a shade 23 located near the focus of the projector lens 24. Thus, an optical axis Z20 approximately corresponds with the respective optical axes of the light source 21, the elliptical reflector 22 and the projector lens 24.
The above-described shade 23 can be configured to include a top surface thereof that substantially corresponds to a horizontal focus curve of the projector lens 24, which intersects the optical axis Z20 at the focus of the projector lens 24. The horizontal focus curve is a horizontal line connecting a number of focus points that allow the projector lens 24 to emit parallel rays. More specifically, FIG. 21 is a schematic cross-section top view depicting the horizontal focus curve FL in relation to the parallel rays emitted from the projector lens 24 via the elliptical reflector 22.
FIG. 21(A) shows a focus F20 emitting the parallel rays to the optical axis Z20 via the projector lens 24 using rays gathered from the range of a radiated angle α of the elliptical reflector 23 to the focus F20 of the projector lens 24 on a horizontal surface including the optical axis Z20. FIGS. 21(B), (C), (D) and (E) show focus F21, F22, F23 and F24 emitting the parallel rays at 10, 20, 30 and 40 degrees to the optical axis Z20, respectively. Actually, the horizontal focus curve FL can be configured to connect the above-described F20-F40 at finer angles.
In the projector headlight 20, a part of the light emitted from the light source 21 directly passes through the projector lens 24 and another part of the light indirectly passes through the projector lens 24 via the elliptical reflector 22. In this case, because the shade 23 can shield upward light, the projector headlight 20 can form the light distribution pattern as shown in FIG. 20(B). In addition, because light reflected at an arbitrary position of the elliptical reflector 22 can be directed in a voluntary direction towards the projector lens 24, a flexible formation of the elliptical reflector 22 may expand on the possibilities for exterior design and appearance as well as possibly expanding the light distribution pattern of the projector headlight 20.
However, because the shade 23 is substantially located along the focus curve FL of the projector lens 24, a contrasting difference between the upper and lower sides of a horizontal cut-off line Pa20 of an oncoming lane and Pb20 of a driving lane in the fundamental light distribution pattern P20 shown in FIG. 20(B) tends to become too clear. When the light-emitting area of the projector headlight 20 becomes smaller and/or the brightness thereof becomes brighter using a high power of light source and the like, the contrasting difference may be especially enhanced and too clear.
Thus, the projector headlight 20 may include a problem in that the excessive contrasting difference thereof causes a decrease of visibility in some cases. In addition, because a contrasting difference between the horizontal cut-off line Pa20 and Pb20 is small, the projector headlight 20 may also include another problem in that the light distribution pattern P20 thereof may be less easily adjusted, especially in a horizontal direction.
The disclosed subject matter relates to a vehicle lamp including a projector headlight for a low beam that addresses and attempts to solve the above-described and other problems characteristics and features. More specifically, the contrasting difference between the upper and lower sides of the horizontal cut-off line Pa20-Pb20 can be reduced so as to conform to a light distribution standard for a headlight. In addition, the contrasting and tonal differences between the horizontal cut-off line Pa20 and Pb20 can become clear and the adjustment of the light distribution pattern can become easy.
Other conventional projector headlights using a top surface of a shade are disclosed in, for instance, patent document No. 2 (Japanese Utility Model Patent Application Laid Open H05-66806), patent document No. 3 (Japanese Patent Application Laid Open JP2006-107955), patent document No. 4 (Japanese Patent Application Laid Open JP2006-294380), etc.
FIG. 22 is a schematic side cross-section view depicting a first conventional projection headlight using a top surface of a shade according to patent document No. 2. The basic structure of the projector headlight 30 shown in FIG. 22 is similar to that of patent document No. 1 shown in FIG. 20(A). However, the shade 33 which includes a flat reflex plate thereon is different from that of patent document No. 1. The shade 33 can create an upward light by reflecting light emitted from a light source 31 via a reflector 32 on the flat reflex plate thereof.
Thus, because the upward light can illuminate above the horizontal cut-off line via a projector lens 34, it can be easy to confirm the presence of a traffic sign and the like located above the light distribution pattern of the projector headlight 30. However, the contrasting difference between the upper and lower sides of the horizontal cut-off line cannot be reduced and the contrasting difference between the horizontal cut-off line Pa20 and Pb20 may also not be clear.
FIG. 23(A) is a schematic side cross-section view depicting a second conventional projection headlight using a top surface of a shade according to patent document No. 3 and FIG. 23(B) is a schematic diagram showing a fundamental light distribution pattern for driving on the left side formed by the headlight of FIG. 23(B). The basic structure of the projector headlight 40 shown in FIG. 23(A) can be similar to that of patent document No. 1 shown in FIG. 20(A). However, the projector headlight 40 that includes a secondary reflector 43 in place of a shade is essentially different from the structure of headlight of patent document No. 1.
Because the secondary reflector 43 slopes down in a direction towards the projector lens 44, the projector headlight 40 can emit a downward light L40 via a projector lens 44 by reflecting light emitted from light source 41 via reflector 42 on the secondary reflector 43. Thus, when a non high-brightness chip such as a single LED chip is used as the light source 41, the projector headlight 40 can form a hot zone H40 (the brightest portion) using the downward light L40 in a light distribution pattern P40 shown in FIG. 23(B).
Thus, the structure disclosed in patent document No. 3 may be useful when using an LED chip and the like as the light source 41. However, the contrasting difference between the upper and lower sides of a horizontal cut-off line Pa40-Pb40 may not be able to be reduced and the contrasting difference between the horizontal cut-off line Pa40 and Pb40 may not become clear.
FIG. 24(A) is a schematic side cross-section view depicting another conventional projection headlight using a top surface of a shade according to patent document No. 4 and FIG. 24(B) is a schematic diagram showing a fundamental light distribution pattern for driving on the left side formed by the headlight of FIG. 24(A). The basic structure of the projector headlight 50 shown in FIG. 24(A) is also similar to that of patent document No. 1 shown in FIG. 20(A). However, the projector headlight 50 that includes a top flat surface of a shade 53 is essentially different from that of patent document No. 1 for several reasons as set forth below.
Because the top flat surface of the shade 53 includes a flat reflector located at a position closer in direction towards a reflector 52 than a focus of a projector lens 54, the projector headlight 50 can emit an upward light L50 by reflecting light emitted from light source 51 via the reflector 52 on the flat reflector of the shade 53. Thus, the projector headlight 50 can gather the upward light L50 via the projector lens 54 at a bright zone H50 underneath a horizontal cut-off line Pa50-Pb50 in a light distribution pattern P50 shown in FIG. 24(B).
Therefore, the structure disclosed in patent document No. 4 may be useful with respect to light efficiency. However, the contrasting difference between the upper and lower sides of the horizontal cut-off line Pa50-Pb50 is generally not reduced but rather increased, and the contrasting difference between the horizontal cut-off line Pa50 and Pb50 may not become clear.
The above-referenced Patent Documents are listed below.    1. Patent document No. 1: Japanese Patent No. 2696745    2. Patent document No. 2: Japanese Utility Model Patent Application Laid Open H05-66806    3. Patent document No. 3: Japanese Patent Application Laid Open JP2006-107955    4. Patent document No. 4: Japanese Patent Application Laid Open JP2006-294380
The disclosed subject matter has been devised to consider the above and other problems, characteristics and features. Thus, an embodiment of the disclosed subject matter can include a vehicle lamp including a projector headlight for a low beam having a favorable light distribution pattern that can conform to a light distribution standard headlights with respect to a contrast difference between the upper and lower sides of a horizontal cut-off line. In this case, if the horizontal cut-off line has a continuous blur portion, the adjustment of the light distribution pattern may become difficult after the projector headlight is attached to a vehicle lamp and the like. However, according to one aspect of the disclosed subject matter, a vehicle lamp projector headlight can have a light distribution pattern that is easily adjusted.